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Multiple ecosystem functions need to be considered simultaneously to manage and protect the several ecosystem services that are essential to people and their environments. Despite this, cost effective, tangible, relatively simple and globally relevant methodologies to monitor in situ soil multifunctionality, that is, the provision of multiple ecosystem functions by soils, have not been tested at the global scale. We combined correlation analysis and structural equation modelling to explore whether we could find easily measured, field-based indicators of soil multifunctionality (measured using functions linked to the cycling and storage of soil carbon, nitrogen and phosphorus). To do this, we gathered soil data from 120 dryland ecosystems from five continents. Two soil surface attributes measured in situ (litter incorporation and surface aggregate stability) were the most strongly associated with soil multifunctionality, even after accounting for geographic location and other drivers such as climate, woody cover, soil pH and soil electric conductivity. The positive relationships between surface stability and litter incorporation on soil multifunctionality were greater beneath the canopy of perennial vegetation than in adjacent, open areas devoid of vascular plants. The positive associations between surface aggregate stability and soil functions increased with increasing mean annual temperature. Synthesis and applications. Our findings demonstrate that a reduced suite of easily measured in situ soil surface attributes can be used as potential indicators of soil multifunctionality in drylands world-wide. These attributes, which relate to plant litter (origin, incorporation, cover), and surface stability, are relatively cheap and easy to assess with minimal training, allowing operators to sample many sites across widely varying climatic areas and soil types. The correlations of these variables are comparable to the influence of climate or soil, and would allow cost-effective monitoring of soil multifunctionality under changing land-use and environmental conditions. This would provide important information for evaluating the ecological impacts of land degradation, desertification and climate change in drylands world-wide. Fil: Eldridge, David J.. University of New South Wales; Australia Fil: Delgado Baquerizo, Manuel. Universidad Rey Juan Carlos; España Fil: Quero, José L.. Universidad de Córdoba; España Fil: Ochoa, Victoria. Universidad Rey Juan Carlos; España. Universidad de Alicante; España Fil: Gozalo, Beatriz. Universidad Rey Juan Carlos; España. Universidad de Alicante; España Fil: García Palacios, Pablo. Universidad Rey Juan Carlos; España Fil: Escolar, Cristina. Universidad Rey Juan Carlos; España Fil: García Gómez, Miguel. Universidad Politécnica de Madrid; España Fil: Prina, Aníbal. Universidad Nacional de La Pampa; Argentina Fil: Bowker, Mathew A.. Northern Arizona University; Estados Unidos Fil: Bran, Donaldo Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche; Argentina Fil: Castro, Ignacio. Universidad Experimental Simón Rodríguez; Venezuela Fil: Cea, Alex. Universidad de La Serena; Chile Fil: Derak, Mchich. No especifíca; Fil: Espinosa, Carlos I.. Universidad Técnica Particular de Loja; Ecuador Fil: Florentino, Adriana. Universidad Central de Venezuela; Venezuela Fil: Gaitán, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Suelos; Argentina. Universidad Nacional de Luján. Departamento de Tecnología; Argentina Fil: Gatica, Mario Gabriel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Biología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Gómez González, Susana. Universidad de Cádiz; España Fil: Ghiloufi, Wahida. Université de Sfax; Túnez Fil: Gutierrez, Julio R.. Universidad de La Serena; Chile Fil: Guzman, Elizabeth. Universidad Técnica Particular de Loja; Ecuador Fil: Hernández, Rosa M.. Universidad Experimental Simón Rodríguez; Venezuela Fil: Hughes, Frederic M.. Universidade Estadual de Feira de Santana; Brasil Fil: Muiño, Walter. Universidad Nacional de La Pampa; Argentina Fil: Monerris, Jorge. No especifíca; Fil: Ospina, Abelardo. Universidad Central de Venezuela; Venezuela Fil: Ramírez, David A.. International Potato Centre; Perú Fil: Ribas Fernandez, Yanina Antonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Romão, Roberto L.. Universidade Estadual de Feira de Santana; Brasil Fil: Torres Díaz, Cristian. Universidad del Bio Bio; Chile Fil: Koen, Terrance B.. No especifíca; Fil: Maestre, Fernando T.. Universidad Rey Juan Carlos; España. Universidad de Alicante; España

One of the most important changes taking place in drylands worldwide is the increase of the cover and dominance of shrubs in areas formerly devoid of them (shrub encroachment). A large body of research has evaluated the causes and consequences of shrub encroachment for both ecosystem structure and functioning. However, there are virtually no studies evaluating how shrub encroachment affects the ability of ecosystems to maintain multiple functions and services simultaneously (multifunctionality). We aimed to do so by gathering data from ten ecosystem functions linked to the maintenance of primary production and nutrient cycling and storage (organic C, activity of β-glucosidase, pentoses, hexoses, total N, total available N, amino acids, proteins, available inorganic P and phosphatase activity), and summarizing them in a multifunctionality index (M). We assessed how climate, species richness, anthropic factors (distance to the nearest town, sandy and asphalted road, and human population in the nearest town at several historical periods) and encroachment by sprouting shrubs impacted both the functions in isolation and M along a regional (ca. 350 km) gradient in Mediterranean grasslands and shrublands dominated by a non-sprouting shrub. Values of M were higher in those grasslands and shrublands containing sprouting shrubs (43% and 62%, respectively). A similar response was found when analyzing the different functions in isolation, as encroachment by sprouting shrubs increased functions by 2%–80% compared to unencroached areas. Encroachment was the main driver of changes in M along the regional gradient evaluated, followed by anthropic factors and species richness. Climate had little effects on M in comparison to the other factors studied. Similar responses were observed when evaluating the functions in isolation. Overall, our results showed that M was higher at sites with higher sprouting shrub cover, longer distance to roads and higher perennial plant species richness. Our study is the first documenting that ecosystem multifunctionality in shrublands is enhanced by encroaching shrubs differing in size and leaf attributes. Our findings reinforce the idea that encroachment effects on ecosystem functioning cannot be generalized, and that are largely dependent on the traits of the encroaching shrub relative to those of the species being replaced.

International audience; 1. Habitat filtering (HF, trait convergence) and niche differentiation (ND, trait divergence) are known to impact upon plant community structure. Both processes integrate individual responses to the abiotic environment and biotic interactions. Thus, it is difficult to clearly identify the underlying abiotic and biotic factors that ultimately impact community structure by looking at community-level patterns of trait divergence or convergence alone. 2. We used a functional trait-based and multiscale approach to assess how biotic interactions and aridity determine the functional structure of semi-arid shrublands sampled along a large aridity gradient in Spain. At the regional scale, we investigated functional differences among species (axes of specialization) to identify important traits for community assembly. At the community scale, we evaluated the relative impact of HF and ND on community structure using a null model approach. Finally, at the plant neighbourhood scale, we evaluated the impact of biotic interactions on community structure by investigating the spatial patterns of trait aggregation. 3. The shrub species surveyed can be separated along four axes of specialization based on their above-ground architecture and leaf morphology. Our community scale analysis suggested that the functional structure of semi-arid communities was clearly non-random, HF and ND acting independently on different traits to determine community structure along the aridity gradient. At the plant neighbourhood scale, the spatial distribution of species was also clearly not random, suggesting that competition and facilitation impacted on the observed changes in the functional diversity of shrubland communities along the aridity gradient. 4. Synthesis: Our results demonstrated that HF and ND acted simultaneously on independent traits to jointly determine community structure. Most importantly, our multiscale approach suggested that competition and facilitation interplayed with aridity to determine this structure. Competition appeared to be constant along the aridity gradient and explained the high functional diversity observed in semi-arid shrublands. Facilitation affected subordinate and rare species and, thus, may act to enhance the biodiversity of these ecosystems. Finally, the framework employed in our study allows moving forward from the examination of patterns to the development of mechanistic traitbased approaches to study plant community assembly.

Global Ecosystem Analysis The relationship between species richness and the functional properties of their ecosystems has often been studied at small scales in experimental plots. Maestre et al. (p. 214 ; see the Perspective by Midgley ) performed field measurements at 224 dryland sites from six continents and assessed 14 ecosystem functions related to carbon, nitrogen, and phosphorus cycling. Positive relationships were observed between perennial plant species richness and ecosystem functionality. The relative importance of biodiversity was found to be as large as, or larger than, many key abiotic variables. Thus, preservation of plant biodiversity is important to buffer negative effects of climate change and desertification in drylands, which collectively cover 41% of Earth's land surface and support over 38% of the human population.

A substantial part of current research efforts on desertification are devoted to establish monitoring systems to evaluate the status of natural resources and the onset of desertification processes. Methodologies based on ground-collected soil and plant indicators are being increasingly used for this aim because they are affordable yet do not compromise accuracy. Despite their inherent value, these methods have limitations regarding the extent of the area that can be monitored using them. Such limitations can be overcome combining field-based approaches with remote sensing data, which allow the establishment of monitoring programs over large areas. In this article we tested the relationship between a field methodology based on indicators of ecosystem functioning, the landscape function analysis (LFA), and a vegetation index (NDVI) obtained from satellite images of the ASTER sensor using data gathered in Stipa tenacissima steppes from central Spain. LFA uses soil surface indicators to assess the condition of a given ecosystem by producing three numerical indices (stability, infiltration and nutrient cycling) reflecting the status of basic soil functions. We found a significant positive linear relationship between the NDVI, the three LFA indices and some key structural attributes of vegetation related to the cover of perennial plants. Our results indicate that NDVI can be used as a surrogate of ecosystem functioning in semi-arid Mediterranean steppes, and thus can be a helpful index to monitor the functional status of large areas in these ecosystems, and the possible onset of desertification processes.

Understanding how intraspecific trait variability (ITV) responds to both abiotic and biotic constraints is crucial to predict how individuals are assembled in plant communities, and how they will be impacted by ongoing global environmental change. Three key functional traits [plant height, leaf area (LA) and specific leaf area (SLA)] were assessed to quantify the range of ITV of four dominant plant species along a rainfall gradient in semi-arid Mediterranean shrublands. Variance partitioning and confirmatory multilevel path analyses were used to assess the direct and indirect effects of rainfall, space limitation (crowding) and neighbouring plant traits on ITV. The direct effect of the local neighbourhood on the trait values of subordinate individuals was as strong as the effect of rainfall. The indirect effect of rainfall, however, mediated by the effect of the local neighbourhood on the trait values of subordinate individuals, was weak. Rainfall decreased the height and SLA of subordinate individuals, but increased their LA. Neighbouring plant traits were just as strong predictors as crowding in explaining changes in ITV.Synthesis. Our study provides a framework to disentangle the direct effects of abiotic factors and their indirect effects on ITV mediated by the local neighbourhood. Our results highlight that abiotic and biotic constraints are both substantial sources of trait variations at the individual level, and can blur processes underlying changes in ITV. Considering and disentangling combined sources with an individual perspective would help to refine our predictions for community assembly and functional ecology.

While much is known about the factors that control each component of the terrestrial nitrogen (N) cycle, it is less clear how these factors affect total N availability, the sum of organic and inorganic forms potentially available to microorganisms and plants. This is particularly true for N-poor ecosystems such as drylands, which are highly sensitive to climate change and desertification processes that can lead to the loss of soil nutrients such as N. We evaluated how different climatic, abiotic, plant and nutrient related factors correlate with N availability in semiarid Stipa tenacissima grasslands along a broad aridity gradient from Spain to Tunisia. Aridity had the strongest relationship with N availability, suggesting the importance of abiotic controls on the N cycle in drylands. Aridity appeared to modulate the effects of pH, plant cover and organic C (OC) on N availability. Our results suggest that N transformation rates, which are largely driven by variations in soil moisture, are not the direct drivers of N availability in the studied grasslands. Rather, the strong relationship between aridity and N availability could be driven by indirect effects that operate over long time scales (decades to millennia), including both biotic (e.g. plant cover) and abiotic (e.g. soil OC and pH). If these factors are in fact more important than short-term effects of precipitation on N transformation rates, then we might expect to observe a lagged decrease in N availability in response to increasing aridity. Nevertheless, our results suggest that the increase in aridity predicted with ongoing climate change will reduce N availability in the Mediterranean basin, impacting plant nutrient uptake and net primary production in semiarid grasslands throughout this region.

Dryland vegetation is characterized by discrete plant patches that accumulate and capture soil resources under their canopies. These “fertile islands” are major drivers of dryland ecosystem structure and functioning, yet we lack an integrated understanding of the factors controlling their magnitude and variability at the global scale. EEA Bariloche Fil: Ochoa-Hueso, Raúl. Universidad Autónoma de Madrid. Department of Ecology; España Fil: Eldridge, David J. University of New South Wales. School of Biological, Earth and Environmental Sciences; Australia Fil: Delgado-Baquerizo, Manuel. University of Colorado. Cooperative Institute for Research in Environmental Sciences; Estados Unidos. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España Fil: Soliveres, Santiago. University of Bern. Institute of Plant Sciences; Suiza Fil: Bowker, Matthew A. Northern Arizona University. School of Forestry; Estados Unidos Fil: Gross, Nicolás. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España. Institut Nationale de la Recherche Agronomique; Francia. Université La Rochelle. Centre d’étude biologique de Chizé; Francia Fil: Le Bagousse-Pinguet, Yoann. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España Fil: Quero, José L. Universidad de Córdoba. Escuela Técnica Superior de Ingeniería Agronómica y de Montes. Departamento de Ingeniería Forestal: España Fil: García-Gómez, Miguel. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España Fil: Valencia, Enrique. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España Fil: Arredondo, Tulio. Instituto Potosino de Investigación Científica y Tecnológica. División de Ciencias Ambientales; México Fil: Beinticinco, Laura. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina Fil: Bran, Donaldo Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentina Fil: Cea, Alex. Universidad de La Serena. Departamento de Biología; Chile Fil: Coaguila, Daniel. Instituto de Ensino Superior de Rio Verde; Brasil Fil: Dougill, Andrew J. University of Leeds. School of Earth and Environment; Gran Bretaña Fil: Espinosa, Carlos I. Universidad Técnica Particular de Loja. Departamento de Ciencias Naturales; Ecuador Fil: Gaitan, Juan Jose. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Suelos; Argentina Fil: Guuroh, Reginald T. University of Cologne. Botanical Institute. Range Ecology and Range Management Group; Alemania. CSIR-Forestry Research Institute of Ghana; Ghana Fil: Guzmán, Elizabeth. Universidad Técnica Particular de Loja. Departamento de Ciencias Naturales; Ecuador Fil: Gutiérrez, Julio R.. Universidad de La Serena. Departamento de Biología; Chile. Centro de Estudios Avanzados en Zonas Áridas (CEAZA); Chile. Instituto de Ecología y Biodiversidad; Chile Fil: Hernández, Rosa M. Universidad Experimental Simón Rodríguez. Centro de Agroecología Tropical. Laboratorio de Biogeoquímica; Venezuela Fil: Huber-Sannwald, Elisabeth. Instituto Potosino de Investigación Científica y Tecnológica. División de Ciencias Ambientales; México Fil: Jeffries, Thomas. Western Sydney University. Hawkesbury Institute for the Environment; Australia Fil: Linstädter, Anja. University of Cologne. Botanical Institute. Range Ecology and Range Management Group; Alemania Fil: Mau, Rebecca L. Northern Arizona University. Center for Ecosystem Science and Society: Estados Unidos Fil: Monerris, Jorge. Université du Québec à Montréal. Pavillon des Sciences Biologiques. Département des Sciences Biologiques; Canadá Fil: Prina, Anibal. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina Fil: Pucheta, Eduardo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Biología; Argentina Fil: Stavi, Ilan. Dead Sea and Arava Science Center, Israel Fil: Thomas, Andrew. Aberystwyth University. Department of Geography and Earth Sciences; Gran Bretaña Fil: Zaady, Eli. Agricultural Research Organization. Gilat Research Center. Natural Resources; Israel Fil: Singh, Brajesh K. Western Sydney University. Hawkesbury Institute for the Environment; Australia. Western Sydney University. Global Centre for Land-Based Innovation; Australia Fil: Maestre, Fernando T. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España